Cannot build extension with .mm file for windows

Hi, I have a generic extension for my project called NativeSupport.

As you might guess, it handles native support for various platforms. My code has a lot of:;

Inside of my NativeSupport functions I break down by platform:
if android
else if ios

Unfortunately when I try to build this extension for windows I get this error:
"Command line warning D9024 : unrecognized source file type ‘.common/’

I know .mm is for objective C, but that file would never be needed for use in the windows environment.
How do I get windows to build this? and why was it never a problem for android?

Hard to say, it looks like you include the mm file when you shouldn’t,
could you share your build.xml?